1. Field of the Invention
The invention relates in general to a refrigerant expansion apparatus, and more particularly to a refrigerant floating expansion apparatus.
2. Description of the Related Art
Refrigeration and air-conditioning system has become a necessity to people in their everyday life. Particularly as industrialization is highly developed, the need for large-sized refrigerating/air-conditioning system increases accordingly. However, the large-sized refrigerating/air-conditioning system lacks of preferred expansion apparatuses. As the refrigeration system is now systematized and new technologies such as multi-stage adjustment and variable speed driven compressor are adopted, manufacturers are even more in need of suitable expansion apparatuses.
Along with the development of the refrigeration system, various types of expansion apparatus such as orifice expansion apparatus, short tube expansion apparatus, thermal expansion apparatus, and electronic expansion apparatus are provided. However, these expansion apparatuses have respective restrictions. For example, the orifice expansion apparatus and short tube expansion apparatus are applicable to most refrigeration systems but only have a fixed pressure drop mechanism and the expansion ability can not be adjusted according to system loads, therefore refrigeration systems adopting such types of expansion apparatus have poor performance in terms of stability, energy saving and cost in maintenance and repair. Thermal expansion apparatus and electronic expansion apparatus are most expensive as compared to the previous ones; particularly the electronic expansion apparatus is in the highest price among all types of expansion apparatus. Moreover, the thermal or electronic expansion apparatus can only be applied to a refrigeration system with small load, and a plurality of the thermal or electronic expansion apparatuses must be connected in serial or parallel if the system load is large, hence incurring higher manufacturing cost and complexity of the system.
Refrigerant expansion apparatus is one of the four main apparatuses (compression apparatus, condensing apparatus, evaporation apparatus and expansion apparatus) in a refrigeration system, and the types of the expansion apparatus is selected according to the type and capacity of the system. For example, a medium or small-sized refrigeration system always adopts thermal expansion apparatus or electronic expansion apparatus. Due to the type and cost of refrigerant, the two expansion apparatus only provide up to 500 refrigeration tons. The refrigeration system above 500 refrigeration tons uses the orifice or floating expansion apparatus because the two expansion apparatuses are not restricted by the types of refrigerant and the capacity of refrigeration system.
As disclosed in Taiwanese Patent Publication No. M276185 “Modified Structure For Control Valve Of Refrigerant Float Ball”, the modified structure includes a control valve set and a float ball component. By controlling the vertical position of the float ball, a valve is enabled to open or close. The valve is in U-shaped, and the refrigerant entrance hole is symmetric with the valve seat, so that the flow of the refrigerant supply is controlled. The float ball and the valve seat are linked by a lever. The size of the refrigerant entrance hole is adjusted by the floating power and leverage of the float ball. However, as the floating power of the float ball is hard to control and the float ball may drift with the refrigerant, the valve seat is thus difficult to maintain at the middle position. Consequently, the supply flow of the refrigerant is affected and the valve seat may even be engaged.
According to American Patent Publication No. U.S. Pat. No. 5,285,653 “Refrigerant Flow Control Device”, the size of the opening on the standpipe is controlled when a float surrounding the standpipe moves up and down. Gas is infused into the underneath of the float via an air passageway for controlling the height of float. Meanwhile, there is a mesh surrounding the float for allowing the fluid to pass through. However, such apparatus controls the volume of gas entering the passageway by way of a control valve, making the apparatus more complicated.
American Patent Publication No. U.S. Pat. No. 5,009,079 “Refrigerant Flow Control Device” also controls the size of the opening on the standpipe when the float surrounding the standpipe moves up and down. In the operation procedure of the apparatus, if the float of the apparatus falls to the bottom of the standpipe, the float will completely cover the opening of the standpipe. Before the next operation of the apparatus starts, a large force must be applied to the float to lift the float for exposing the opening of the standpipe to restore the flow.